In a surgical operation on a cardiocirculatory system that requires an extracorporeal circulation, for the purposes of obtaining a bloodless operative field of view and achieving a manipulation of the surgical operation simply, a venous reservoir generally is used in an extracorporeal circulation circuit for temporarily storing blood from a body. Recently, recognition of less invasive surgical operations has been increased, so that an extracorporeal circulation system with a small incursion into the blood has been required.
Generally used venous reservoirs are roughly divided into: open-type venous reservoirs having hard outer shells; and flexible closed-type venous reservoirs that have flexible outer shells and are closed. The open-type venous reservoir is excellent in a function of removing air bubbles that are mixed into blood, and can show a blood storage capacity precisely. However, the open-type venous reservoir exposes blood to outside air, which is likely to cause an effect on the blood such as blood coagulation. On the other hand, the flexible closed-type venous reservoir basically does not expose blood to outside air, which causes a smaller effect on the blood. However, the flexible closed-type venous reservoir has problems of difficulty of showing its blood storage capacity, removing air bubbles and the like. An example of the closed-type venous reservoir having a means for solving these problems is disclosed in Patent Document 1.
In the dosed-type venous reservoir, a closed space is formed by an outer wall that forms a housing of the venous reservoir. A septum member made of a flexible material is provided in the outer wall, and the closed space is partitioned by the septum member into a blood storage chamber and a volume adjusting chamber. In the blood storage chamber, an inflow port and an outflow port are provided. The inflow port is used for introducing blood, and the outflow port is used for ejecting blood. In the volume adjusting chamber, an adjusting port is provided, which is used for injecting and ejecting an adjusting liquid for volume adjustment.
By injecting and ejecting the adjusting liquid for the volume adjustment with respect to the volume adjusting chamber through the adjusting port, an amount of the adjusting liquid to be stored in the volume adjusting chamber is changed. Thereby, the septum member is moved, thus changing the volume of the volume adjusting chamber, and accordingly, changing the capacity of the blood storage chamber. In addition, the volume of the volume adjusting chamber can be known by measuring a transferring amount of the adjusting liquid.
Patent document 1: JP 2000-299 A